8.3 Phases of Matter

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8.3 Phases of Matter

• On Earth, pure substances are usually found as
  solids, liquids, or gases.
• These are called phases of matter.

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8.3 The phases of matter

• A solid holds its shape and does not flow.
• The molecules in a solid vibrate in place, but on
  average, dont move far from their places.

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8.3 The phases of matter

• A liquid holds its volume, but does not hold its
  shapeit flows.
• Liquids flow because the molecules can move
  around.

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8.3 The phases of matter

• A gas flows like a liquid, but can also expand or
  contract to fill a container.
• A gas does not hold its own volume or shape.
• The molecules in a gas have enough energy to
  completely break away from each other.

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8.3 The phases of matter

• When they are close together, molecules are
  attracted through intermolecular forces.

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8.3 The phases of matter

• The forces in chemical bonds are stronger than
  intermolecular forces.

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8.3 Intermolecular forces
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8.3 Intermolecular forces

• Within all matter, there is a constant
  competition between temperature and
  intermolecular forces.
• When temperature wins the competition, molecules
  fly apart and you have a gas.
• When intermolecular forces win the competition,
  molecules clump tightly together and you have a
  solid.

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8.3 Melting and boiling

• The melting point is the temperature at which a
  substance changes from a solid to a liquid.

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8.3 Melting and boiling

• The temperature at which a liquid becomes a gas
  is called the boiling point.

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Notice temperature is constant while ice melts!
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8.3 Melting and boiling points ofcommon
substances

• Materials have a wide range of melting and
  boiling points.

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8.3 Sublimation

• Sometimes a solid can change directly to a gas
  when heat energy is added.
• This process is called sublimation.

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8.3 Plasma

• In the plasma phase, matter becomes ionized as
  electrons are broken loose from atoms.
• The Sun is made of plasma, as is most of the
  universe, including the Orion nebula.

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